In minimally invasive medical intervention, interventional devices such as needles, guide wires, sheaths and catheters are inserted in a patient in order to find and measure the relevant anatomy of the patient on one hand and to treat or place a medical instrument such as a stent on the other hand. In such medical applications, the part of the interventional devices inserted into the patient either must be sterile during the entire treatment duration or should only be contaminated with fluids and tissue from the patient himself.
When the interventional device, in particular a needle, guide wire or catheter, is equipped with a sensor or activator, one or more connections, for instance electrical wires or optical fibers, must be made to transmit the information or power to or from a controller or interrogator placed in the non-sterile zone away from the patient. This means that somewhere along the information/power transmission line, the sterile zone meets the non-sterile zone. Consequently, a proper management of sterility is required.
This sterility management is also important for Optical Shape Sensing (OSS), which uses backscattered light, for instance infrared (IR) light, at distributed positions along an optical sensor to determine the strain along the length of this sensor. From this strain measurement the corresponding shape of that optical sensor can be reconstructed. When the optical sensor is incorporated into a flexible medical device such as a guide wire or a catheter, this technology can provide the shape of the medical device within the patient body. The Optical Shape Sensing (OSS) technology is also called Fiber-optical RealShape (FORS) technology.
During an OSS procedure, an optical connection needs to be established between an optical sensor on one hand, which is inserted in a patient and must be sterile; and a patch cord, a controller or an interrogator on the other hand, which is placed in the non-sterile zone away from the patient. Upon making the optical connection, the sterile proximal end of the optical sensor comes in contact with a non-sterile patch cord, a mating sleeve of a controller or interrogator, thereby becoming non-sterile. During a medical procedure a sterility problem may arise when the optical waveguide connected to the patch cord, controller or interrogator needs to be disconnected and the now non-sterile proximal end of the optical sensor needs to enter the sterile zone or when medical devices such as catheters, guide wires or sheaths need to slide over the optical sensor. The optical sensor or optical waveguide are for instance optical fibers. The medical device sliding over the optical sensor and having direct contact with the inner body of the patient therefore transports any contamination into the body of the patient.
One way to solve the sterility problem is to introduce a sterile barrier between the sterile proximal end of the optical sensor and the non-sterile patch cord, controller or interrogator. U.S. Pat. No. 5,949,929 discloses a rotary optical connection system for use with a fiber-optic imaging catheter. The system comprises a stationary sterile shield. The stationary sterile shield is made of a biocompatible injection-molded elastomer such as polyethylene, polyolefin, PEBAX. Further, the sterile shield disclosed therein does not protect the optical interfaces at the connection.
In case the sterile barriers are placed in between the optical fibers, the system may be disadvantageous due to high optical insertion losses. In order to reduce the optical insertion loss, the sterile barrier needs to be made very thin so that it becomes rather fragile and prone to rupture. Further, the goal of lowering the insertion loss also poses stringent requirements on the relative alignment of the optical fibers on both the sterile and the non-sterile sides. In particular, the relative alignment has to be a fraction of the mode field diameter which is in the order of several micrometers.
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